1. Technical Field
The present invention relates generally to heating devices used for heating an intravenous fluid during delivery of the intravenous fluid to a patient in a hospital environment. More particularly, the present invention relates to an intravenous fluid heat exchanger used in conjunction with a heated gaseous fluid being delivered to an inflatable, thermal blanket covering a patient to warm intravenous fluid being administered to the patient.
2. Background Art
It is often desirable to control the temperature of a patient in a hospital setting to prevent a patient's body temperature from dropping below a desired temperature. In order to control the patient's body temperature, it is well known in the medical field to cover a patient with a thermal blanket having a temperature-controlled medium flowing there through to substantially surround the patient with a warm environment. One such thermal blanket is disclosed in U.S. Pat. No. 4,777,802 issued to Feher, where heated air is blown into a blanket used to cover a patient. The blanket includes an outer layer impermeable to air and an inner air-permeable layer, where the heated air passes through the inner air-permeable layer to flow over and heat the patient covered by the blanket.
In addition to the outer environment surrounding the patient, a further factor existing in controlling a patient's body temperature involves the administration of intravenous (IV) fluids to a patient in a hospital setting. Many IV fluids are conventionally stored in a cold atmosphere to preserve the IV fluids until they are used in a patient. The injection of cold IV fluids into a patient creates a major source of conductive heat loss within the patient, thus lowering the body temperature of the patient. Therefore, it is common in the medical field to heat IV fluids prior to intravenous injection of the IV fluids into the patient. Examples of such IV fluid heating techniques include immersing the IV fluid in a warm liquid bath or running the IV fluid through a carrier which rests upon an electrical hot plate. However, such prior IV fluid heating techniques are generally inefficient, expensive, or provide inaccurate temperature control of the IV fluid.
In an attempt to overcome some the problems present in prior IV fluid heating techniques, U.S. Pat. No. 5,106,373 issued to Augustine et al. discloses warming intravenously-administered fluids by passing a portion of an IV tube through a thermal blanket as described above having a heated gas flowing there through to warm the exterior of a patient. The portion of the IV tube located within the thermal blanket is positioned in the flow path of the heated gas traveling through the thermal blanket, where thermal energy is transferred from the heated gas to the IV fluid flowing through the thermal blanket. The portion of the IV tube traveling through the thermal blanket is designed to have the same diameter as the rest of the IV tube, so that the flow rate of the IV fluid is not altered as it travels through the portion of the IV tube in the thermal blanket. Since thermal blankets are often used in a hospital setting in order to regulate a patient's body temperature, incorporating an IV fluid warming device into a thermal blanket is quite desirable as it provides a simple, efficient, and cost-effective manner of heating IV fluid without the requiring additional equipment or procedures for warming the IV fluid.
However, the IV fluid warming device disclosed by Augustine et al. does not allow the temperature of the IV fluid to be adequately controlled for the specific requirements of each individual patient. The amount of warming provided to the IV fluid is dependent upon the temperature of the heated gas flowing through the thermal blanket and the surface area of the IV fluid exposed to the increased temperature of the heated gas, which is determined by the inner surface area of the IV tube extending through the thermal blanket. The inner surface area of the IV tube within the thermal blanket of Augustine et al. remains a constant value, so that it would be necessary to change the temperature of the heated gas flowing through the thermal blanket in order to variably control the amount of heat transferred to the IV fluid. However, changing the temperature of the heated to control the temperature of the IV fluid would interfere with system's primary function of heating the body of a patient. Further, in some instances, it is desirable to heat the outside of a person's body using the thermal blanket while only needing to partially heat the IV fluid passing though the thermal blanket. Whereas, the IV fluid warming device of Augustine et al. does not allow for separate control of the temperature of the IV fluid from the temperature of the heated gas passing through the thermal blanket.
Clearly, there is a need for an IV fluid heat exchanger which easily and effectively allows the temperature of the IV fluid to be precisely regulated. Further, there is a need for a temperature-controllable IV fluid heat exchanger which may be readily used in conjunction with a gaseous-heated thermal blanket for providing the heating medium for the IV fluid.